1. Field of the Invention
The present invention relates to an NMR spectrometer and method of NMR measurement and, more particularly, to an NMR spectrometer and method of NMR measurement which can save the amount of deuterated solvent used for NMR locking and which makes it unnecessary to readjust the resolution whenever the sample is exchanged.
2. Description of Related Art
An NMR spectrometer is an instrument producing a static magnetic field in which a sample to be investigated is placed. An RF (radio-frequency) magnetic field orthogonal to the static magnetic field is applied to the sample. Then, a very weak RF magnetic field signal (NMR signal) emanating from the sample is detected. Information about the molecular structure of the sample is extracted from the signal, and the molecular structure of the sample is analyzed.
When an NMR measurement is performed, it is necessary to detect the chemical shift on the order of ppm and thus drift in the static magnetic field is corrected by a technique known as “NMR lock” during the measurement to prevent the drift in the static field. NMR lock is a technique for correcting drift in the static magnetic field by observing an NMR signal arising from a nucleus other than the nucleus under observation (usually, deuterium nucleus (2D)), detecting the amount of shift of the position of the NMR signal originated from the deuterium nucleus due to drift in the static magnetic field, and feeding back a signal corresponding to the shift to the shim coil current used to superimpose a correcting magnetic field on the static magnetic field. Accordingly, in NMR measurement, a deuterium compound (usually, deuterated solvent) is added to the sample to perform NMR locking.
Furthermore, in NMR measurements, the resolution is deteriorated due to inhomogeneity of the strength of the static magnetic field generally caused by the magnetic susceptibility of the sample. Accordingly, whenever a sample is exchanged, the shims are finely adjusted to correct for the inhomogeneity of the static magnetic field strength according to the sample.